This study consists of three projects that examine numerous aspects of the growth and nutrition of children with sickle cell disease (SCD): (1) Longitudinal growth, development, nutritional status, and dietary intake of 150 SCD patients, (birth to 18 years); (2) Energy balance in children (5 to 18 years) with SCD using resting and total energy expenditure and dietary intake while in a usual state of health vs. healthy children; and (3) Energetic cost of acute illness by resting energy expenditure and dietary intake of children with SCD during hospitalization for an acute illness compared to usual state of health. Enrollment and data collection for these three projects have been completed (as of 10/98). We are now in the data management and data analysis phase of the project, which will include use of the GCRC biostatistical services.